This application claims the priority of German patent document 100 46 007.0, filed Sep. 18, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a computer implemented flight control system for an aircraft.
Airplanes with modern flight control systems are part of the technical pioneering achievements of our time. Few technologies incorporate such complexity and such a degree of perfection when converting engineers"" knowledge into the implementation of new systems. However, despite all the sophisticated systems, there are still airplane crashes. After an overall analysis of the flight, the causes an accident are determined, and consequences are established from the crashes in order to eliminate these causes by changed methods and system changes for future flights.
Although these results have made flight traffic safer, there will still be new accidents resulting from new causes as well as from known causes that have not been eliminated. The consequences of the causes are partially known but can occur again because conventional techniques do not allow a proper reaction to the combination of accident causes. This means that the circumstances of the accident may be repeated because the lessons learned from accidents was not sufficiently implemented in the airplanes.
On the other hand, new accidents also occur because of new unpredicted cause combinations. These are combinations which can only be roughly estimated by experts because of an only approximate idea of the system performance.
Furthermore, the system performance may not have been sufficiently included in the analyses, because an occurrence had not been considered possible until the flight accident occurred, in that the cross connections between a system malfunction and human operating behavior had not been analyzed. This system performance had at least not been implemented in a protection or warning system, and in the best of all circumstances reports may exist concerning the effects of the malfunction.
In known computer-based flight control systems, the consequences are evaluated from combinations of obtained flight and system parameters, by implementing existing safety analyses. The latter, however, are not actively integrated in the algorithm of the flight control systems.
Using these flight control systems, the pilot is often unaware of the danger of a flight situation at the critical moment. And even if he is warned, it is not certain that he will recognize the danger in time to perform an accident-avoidance maneuver which is adapted to the situation.
If the pilot is warned at the decisive moment, he will obtain a flood of (important and unimportant) information from which he must draw the correct conclusions, in a high stress situation, under extreme time pressure, sometimes with fatal consequences.
It is an object of the invention to provide a cockpit flight control system which automatically detects safety-critical flight conditions, and supplies advice to the pilot in time for correcting these flight conditions.
This and other objects and advantages are achieved by the flight control system according to the invention, in which an additional computer is provided in the airplane, operating parallel to the flight control. As a vigilant observer, it monitors flight and system parameters. In contrast to the crash recorder, an analysis of the detected data is not deferred to experts on the ground, weeks after a flight accident; rather, the computer automatically and continuously carries out risk estimates during the flight and emits recommendations for actions by the pilot.
As a result of the solution according to the invention, the total expert knowledge is available to the pilot in real time and can therefore provide a basis for decisions about the most important accident-preventing measures. In this case, the system must be capable of implementing the expert knowledge; specifically, precisely in the form in which expert knowledge is available to judge such events.
Advantageously, the flight control system according to the invention uses a fuzzy logic system, based on linguistic rules. Fuzzy systems are very tolerant with respect to faults and range definitions, and are therefore better suitable than stringent threshold values for obtaining a good overview of potential good and bad system conditions. Stringent threshold values will fail at the smallest undefined departure from their definition ranges.
In particular, the most varied flight and system parameters can be linked with the fuzzy logic. Likewise, the problems existing in the known flight control systems concerning warning threshold values are softened, without, however, losing the requisite precision. The latter advantage is achieved according to the invention by a dual assignment of the rules in a conventional manner as well as in the fuzzy logic.
The flight control system according to the invention has an open structure by means of which new knowledge concerning flight accidents or new system trends can be implemented at low expenditures, and in a clear format.